9,584 research outputs found

    Adversarial Sparse-View CBCT Artifact Reduction

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    We present an effective post-processing method to reduce the artifacts from sparsely reconstructed cone-beam CT (CBCT) images. The proposed method is based on the state-of-the-art, image-to-image generative models with a perceptual loss as regulation. Unlike the traditional CT artifact-reduction approaches, our method is trained in an adversarial fashion that yields more perceptually realistic outputs while preserving the anatomical structures. To address the streak artifacts that are inherently local and appear across various scales, we further propose a novel discriminator architecture based on feature pyramid networks and a differentially modulated focus map to induce the adversarial training. Our experimental results show that the proposed method can greatly correct the cone-beam artifacts from clinical CBCT images reconstructed using 1/3 projections, and outperforms strong baseline methods both quantitatively and qualitatively

    Non-damping oscillations at flaring loops

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    Context. QPPs are usually detected as spatial displacements of coronal loops in imaging observations or as periodic shifts of line properties in spectroscopic observations. They are often applied for remote diagnostics of magnetic fields and plasma properties on the Sun. Aims. We combine imaging and spectroscopic measurements of available space missions, and investigate the properties of non-damping oscillations at flaring loops. Methods. We used the IRIS to measure the spectrum over a narrow slit. The double-component Gaussian fitting method was used to extract the line profile of Fe XXI 1354.08 A at "O I" window. The quasi-periodicity of loop oscillations were identified in the Fourier and wavelet spectra. Results. A periodicity at about 40 s is detected in the line properties of Fe XXI, HXR emissions in GOES 1-8 A derivative, and Fermi 26-50 keV. The Doppler velocity and line width oscillate in phase, while a phase shift of about Pi/2 is detected between the Doppler velocity and peak intensity. The amplitudes of Doppler velocity and line width oscillation are about 2.2 km/s and 1.9 km/s, respectively, while peak intensity oscillate with amplitude at about 3.6% of the background emission. Meanwhile, a quasi-period of about 155 s is identified in the Doppler velocity and peak intensity of Fe XXI, and AIA 131 A intensity. Conclusions. The oscillations at about 40 s are not damped significantly during the observation, it might be linked to the global kink modes of flaring loops. The periodicity at about 155 s is most likely a signature of recurring downflows after chromospheric evaporation along flaring loops. The magnetic field strengths of the flaring loops are estimated to be about 120-170 G using the MHD seismology diagnostics, which are consistent with the magnetic field modeling results using the flux rope insertion method.Comment: 9 pages, 9 figures, 1 table, accepted by A&

    Negative-Index Refraction in a Lamellar Composite with Alternating Single Negative Layers

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    Negative-index refraction is achieved in a lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials stacked alternatively. Based on the effective medium approximation, simultaneously negative effective permittivity and permeability of such a lamellar composite are obtained theoretically and further proven by full-wave simulations. Consequently, the famous left-handed metamaterial comprising split ring resonators and wires is interpreted as an analogy of such an ENG-MNG lamellar composite. In addition, beyond the effective medium approximation, the propagating field squeezed near the ENG/MNG interface is demonstrated to be left-handed surface waves with backward phase velocity.Comment: 18 pages, 6 figure

    Effects of relative orientation of the molecules on electron transport in molecular devices

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    Effects of relative orientation of the molecules on electron transport in molecular devices are studied by non-equilibrium Green's function method based on density functional theory. In particular, two molecular devices, with the planer Au7_{7} and Ag3_{3} clusters sandwiched between the Al(100) electrodes are studied. In each device, two typical configurations with the clusters parallel and vertical to the electrodes are considered. It is found that the relative orientation affects the transport properties of these two devices completely differently. In the Al(100)-Au7_7-Al(100) device, the conductance and the current of the parallel configuration are much larger than those in the vertical configuration, while in the Al(100)-Ag3_{3}-Al(100) device, an opposite conclusion is obtained

    Akurasi Sistem Registrasi Kematian dan Penyebab Kematian (Studi Tipikal Sejumlah Daerah di Indonesia) Masih Perlu Banyak Peningkatan: Sistem Registrasi Kematian dan Penyebab Kematian di Beberapa Daerah, Indonesia 2014

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    Death Registrations System and Cause of Death are fundamental in creating demographic andepidemiological measures needed by regional planning in various sectors, such as education,employment and health. The aims of this study are to address the strengths and weaknesses of the Death Registrations System and Causes of Death in several regions in Indonesia; so they will know the areas that require improvement and actions that need to be done. The current system status is determined using a rapid assessment which has been developed by WHO and Health Information Systems Knowledge Hub, from the University of Queensland (2010a). Twenty-five questions were discussed by participants consisting of 2–4 groups of senior staffs responsible for various aspects ofthe Death Registration System and Cause of Death. The assessment was conducted in 13 districts/municipalities in 2014. As a result, there are still some aspects of the function of the system should beimproved. Regions with a high enough value is Surakarta (80%) and Yogyakarta (68%) included in thecategory of moderate or 65–84; functional but not sufficient. The average area with values below 64%,is classified as weak. There are variations in the strength and a weakness of each region. It is importantto develop appropriate strategies to obtain Death Registrations System and Cause of Death better.Keywords: rapid assessment, Death Registrations and Cause of Death, Indonesia
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